It has been conventional for many years to manufacture pneumatic tires from cord fabric made by dipping an array of parallel cords in a resorcinol formaldehyde latex composition and drying the dipped cords under tension, followed by application of unvulcanized rubber. The tires are then built from the rubberized cords and other components, including beads at the edges of the tire structure, and wear resistant treads.
In preparing the rubberized cord fabric, it is sometimes convenient to be able to dip-coat and dry the cords as a separate operation from the rubberizing or application of unvulcanized rubber to the coated cords. However, it has been found that if the dipped and dried cords are exposed for a significant time to the atmosphere or to the sun, the usual rubber compositions will not adhere satisfactorily to the cords. Consequently, it has been the general practice to apply the rubber to the dipped and dried cords immediately in a single operation without interruption, or else to protect the dipped and dried cords by an opaque impervious wrapping during the interval between dip-coating and rubberizing.
In spite of all precautions, some lots of rubberized cord fabric have been found to have inadequate adhesion of rubber to the cords and have had to be scrapped. Moreover, if some operating problem should require temporary interruption of the dipping and drying process so that partly processed material is exposed for an hour or more before it can be rubberized or otherwise protected from exposure, that portion of the material may not bond satisfactorily to the subsequently applied rubber, and if used in manufacture of tires, it might lead to separation and failure of the tires and must, therefore, be cut out and discarded.
Efforts to overcome this difficulty by use of antioxidants or antiozonants have been unsuccessful, and substantial losses have continued to result from inadequate adhesion.
The principal object of this invention, accordingly, is to provide a procedure and materials for making rubberized cord fabric which will result in a uniformly high level of adhesion of the rubber to the cords, and eliminate the losses resulting from scrapping of materials having inadequate adhesion values.